Apparent Motion Research Articles

Morphology and Climatology of Nighttime Periodic Ionospheric TEC Disturbances Associated With MSTIDs Over China

AbstractIn this study, the morphology and climatology of the nighttime periodic disturbances associated with medium‐scale traveling ionospheric disturbances (MSTIDs) are investigated over the entire China sector from January 2014 to August 2017, using data from global navigation satellite systems (GNSS) receivers. Firstly, a comparative case analysis of propagation characteristics reveals the complexity and day‐to‐day variations of nighttime MSTID activity. The main statistical findings indicate that these periodic disturbances predominantly occur during the summer months, with a higher occurrence rate during solar minimum. In summer, the disturbances occur more frequently in regions with lower latitudes (20–35°N) and tend to exhibit an extended duration. In the meantime, some disturbances are also detected at much lower latitudes (<20°N), with noticeable longitudinal differences. Additionally, there are two peaks in the geographic distribution of disturbances, located in the sector of 90–100°E and 105–125°E at lower latitudes, respectively. The distinct spatiotemporal evolution patterns of the two peak disturbance regions suggest that their formation mechanisms should be different. The disturbances in the eastern region exhibit similarities with electrified MSTIDs, which are closely related to Perkins instability, whereas the western disturbance region does not display apparent movement, but exhibits a higher occurrence rate and longer durations, which may be attributed to the frequent upward propagation of GWs in the southeastern region of the Qinghai‐Tibet Plateau.

On the Corotation of Milky Way Satellites: LMC-mass Satellites Induce Apparent Motions in Outer Halo Tracers

Abstract Understanding the physical mechanism behind the formation of a corotating thin plane of satellite galaxies, like the one observed around the Milky Way (MW), has been challenging. The perturbations induced by a massive satellite galaxy, like the Large Magellanic Cloud (LMC), provide valuable insight into this problem. The LMC induces an apparent corotating motion in the outer halo by displacing the inner regions of the halo with respect to the outer halo. Using the Latte suite of Feedback In Realistic Environments cosmological simulations of MW-mass galaxies, we confirm that the apparent motion of the outer halo induced by the infall of a massive satellite changes the observed distribution of orbital poles of outer-halo tracers, including satellites. We quantify the changes in the distribution of orbital poles using the two-point angular correlation function and find that all satellites induce changes. However, the most massive satellites with pericentric passages between ≈30 and 100 kpc induce the largest changes. The best LMC-like satellite analog shows the largest change in orbital pole distribution. The dispersion of orbital poles decreases by 20° during the first two pericentric passages. Even when excluding the satellites brought in with the LMC-like satellite, there is clustering of orbital poles. These results suggest that in the MW, the recent pericentric passage of the LMC should have changed the observed distribution of orbital poles of all other satellites. Therefore, studies of kinematically coherent planes of satellites that seek to place the MW in a cosmological context should account for the existence of a massive satellite like the LMC.

Increased adult movements and decreased juvenile apparent survival of urban crows during COVID-19 lockdowns

The increasing abundance of animal species thriving in urban environments is a source of conflicts with managers and users of public spaces. Although opportunistic urban species often use resources originating from human food leftovers, the potential impact of a reduction in these resources on their demography is hard to quantify. The COVID-19 epidemic, which led many countries to set up lockdowns, gave us the opportunity to estimate the impact of a drastic reduction in such food resources and human activities on the demography of an urban bird population. Based on 7 years (2015–2021) of capture-mark-recapture of carrion crows (Corvus corone) in the city of Paris, France, we used multi-state models to examine the intra-annual (3-month time steps) apparent survival and movement patterns of crows during and outside COVID-19 lockdowns. We showed that the apparent survival of juvenile carrion crows decreased down during lockdown, while adult movements increased during this period, with more adult crows moving out of the urban district. Lockdown modified the demography of this urban crow population, suggesting that the reduction in food resources was sufficient to affect fitness and reduce carrying capacity.

Superluminal Proper Motion in the X-Ray Jet of Centaurus A

The structure of the jet in Cen A is likely better revealed in X-rays than in the radio band, which is usually used to investigate jet proper motions. In this paper, we analyze Chandra Advanced CCD Imaging Spectrometer observations of Cen A from 2000 to 2022 and develop an algorithm for systematically fitting the proper motions of its X-ray jet knots. Most of the knots had an apparent proper motion below the detection limit. However, one knot at a transverse distance of 520 pc had an apparent superluminal proper motion of 2.7 ± 0.4c. This constrains the inclination of the jet to be i < 41° ± 6° and the velocity of this knot to be β > 0.94 ± 0.02. This agrees well with the inclination measured in the inner jet by the Event Horizon Telescope but contradicts previous estimates based on jet and counterjet brightness. It also disagrees with the proper motion of the corresponding radio knot, of 0.8 ± 0.1c, which further indicates that the X-ray and radio bands trace distinct structures in the jet. There are four prominent X-ray jet knots closer to the nucleus, but only one of these is inconsistent with being stationary. A few jet knots also have a significant proper-motion component in the nonradial direction. This component is typically larger closer to the center of the jet. We also detect brightness and morphology variations at a transverse distance of 100 pc from the nucleus.

Molecular Distribution in the Central Region of M87

The central region of M87 has been observed by the Atacama Large Millimeter/submillimeter Array (ALMA) several times to resolve its molecular cloud distribution. We present the ALMA CO(1–0), CO(2–1), and CO(3–2) observations of the M87 circumnuclear region. The CO(1–0) shows emission as well as molecular absorption features toward its nucleus, indicating the existence of cold molecular clouds/gas. ALMA imaging of the CO(1–0) observations show the distribution of molecular clouds toward the nucleus of M87 with a radius of ∼105 pc. The clouds seen in the CO(1–0) are moving with very high velocity and have an apparent motion in the range of −1000 to 3600 km s−1 relative to the central supermassive black hole, which has a systemic velocity of ∼1266 km s−1. The molecular gas mass was estimated to be about 1.08 ± 0.64 × 107 M ⊙ in the central 210 pc of M87. We calculated the optical depths using the absorption lines of the CO(1–0) and CO(2–1). The excitation temperature was estimated to be ∼7.133 ± 0.03 K using the optical depth ratio of the CO(2-1) to CO(1-0). We also found the line-of-sight column density to be ∼2.25 × 1015 cm−2, which corresponds to a hydrogen column density of ∼0.28 × 1020 cm−2.

Maya and Aztec astronomy: Skywatching in prehispanic Mesoamerica

Abstract The Aztecs, Maya and other Mesoamerican peoples achieved advanced knowledge of the regularities of the apparent motion of the Sun, Moon and various planets visible with the naked eye, particularly Venus. Much of this knowledge enabled orientation in space and time and was particularly useful for scheduling agricultural activities. However, since the celestial order is apparently superior to that on Earth, the phenomena observed in the sky were believed to exert influence on earthly affairs. Therefore, the exact astronomical knowledge was intertwined with religious beliefs and ritual performances, and this complex worldview had a prominent role not only in subsistence activities but also in the political ideology of the ruling class. The relevant information is contained in the imagery and hieroglyphic texts in prehispanic manuscripts or codices, mural paintings, sculpted monuments and other archaeological objects, as well as in early colonial written sources and ethnographically documented survivals of prehispanic concepts. Important data are also provided by architectural orientations, most of which were laid out on astronomical grounds, largely referring to the Sun’s positions on the horizon on certain dates.

Dazzling damselfish: investigating motion dazzle as a defence strategy in humbug damselfish (Dascyllus aruanus)

Many animals possess high-contrast body patterns. When moving, these patterns may create confusing or conflicting visual cues that affect a predator’s ability to visually target or capture them, a phenomenon called motion dazzle. The dazzle patterns may generate different forms of optical illusion that can mislead observers about the shape, speed, trajectory and range of the animal. Moreover, it is possible that the disruptive visual effects of the high contrast body patterns can be enhanced when moving against a high contrast background. In this study, we used the humbug damselfish (Dascyllus aruanus) to model the apparent motion cues of its high contrast body stripes against high contrast background gratings of different widths and orientations, from the perspective of a predator. We found with higher frequency gratings, when the background is indiscriminable to a viewer, that the humbugs may rely on the confusing motion cues created by internal stripes. With lower frequency gratings, where the background is likely perceivable by a viewer, the humbugs can rely more on confusing motion cues induced by disruption of edges from both the background and body patterning. We also assessed whether humbugs altered their behaviour in response to different backgrounds. Humbugs remained closer and moved less overall in response to backgrounds with a spatial structure similar to their own striped body pattern, possibly to stay camouflaged against the background and thus avoid revealing themselves to potential predators. At backgrounds with higher frequency gratings, humbugs moved more which may represent a greater reliance on the internal contrast of the fish’s striped body pattern to generate motion dazzle. It is possible that the humbug stripes provide multiple protective strategies depending on the context and that the fish may alter their behaviour depending on the background to maximise their protection.

Exploring the impact of apparent motion in V1 retinotopic representations and behavioral correlates in primates

Exploring the impact of apparent motion in V1 retinotopic representations and behavioral correlates in primates

Investigating the breadth and strength of perceptual control of Illusory Apparent Motion

Investigating the breadth and strength of perceptual control of Illusory Apparent Motion

Individual differences in long-range visual apparent motion

Individual differences in long-range visual apparent motion

Ambiguous apparent motion in exchanging disks

A large and a small disk with radii R and r, side by side, exchange positions repetitively at 1.33 Hz. The motion is ambiguous. If r/ R &lt; 0.8 then observers perceive a single large disk jumping back and forth across a small static disk. But if r/ R &gt; 0.8, observers perceive two static disks that expand and contract in counter phase, with no motion across the gap between the disks. Observers respond to the movement of the centroid, which is greatest when r/ R &lt; 0.8.

Bioclimatic analysis of three buildings by Gilberto Gatto Sobral. Study case Universidad Central del Ecuador

The bioclimatic quality of three buildings by architect Gilberto Gatto Sobral at Universidad Central del Ecuador was evaluated with two objectives: to find problems that might affect users’ health and productivity, and to establish if climate had a significant role in the design of these buildings The buildings included two faculties: Law and Economics, and the General Administration. Bioclimatic quality was established by comparing existing levels of temperature, relative humidity, and natural light against comfort standards and the local climate. Data were measured over two years in space samples using data loggers. It was concluded that all buildings have spaces outside of comfort being too cold and dark; and climate played a minor role because despite attempts to control natural light, the thermal behavior of materials and the sun’s apparent movement were ignored.

Evolution of the Termination Region of the Parsec-scale Jet of 3C 84 Over the Past 20 yr

We present the kinematics of the parsec-scale jet in 3C 84 from 2003 November to 2022 June observed with the Very Long Baseline Array at 43 GHz. We find that the C3 component, a bright feature at the termination region of the jet component ejected from the core in 2003, has maintained a nearly constant apparent velocity of 0.259 ± 0.003c over the period covered by observations. We observe the emergence of four new subcomponents from C3, each exhibiting apparent speeds higher than that of C3. Notably, the last two subcomponents exhibit apparent superluminal motion, with the fastest component showing an apparent speed of 1.22 ± 0.14c. Our analysis suggests that a change in viewing angle alone cannot account for the fast apparent speeds of the new subcomponents, indicating that they are intrinsically faster than C3. We identify jet precession (or reorientation), a jet–cloud collision, and magnetic reconnection as possible physical mechanisms responsible for the ejection of the new subcomponents.

Risk factors and outcomes associated with systolic dysfunction following traumatic brain injury.

Systolic dysfunction has been observed following isolated moderate-severe traumatic brain injury (Ims-TBI). However, early risk factors for the development of systolic dysfunction after Ims-TBI and their impact on the prognosis of patients with Ims-TBI have not been thoroughly investigated. A prospective observational study among patients aged 16 to 65 years without cardiac comorbidities who sustained Ims-TBI (Glasgow Coma Scale [GCS] score ≤12) was conducted. Systolic dysfunction was defined as left ventricular ejection fraction <50% or apparent regional wall motion abnormality assessed by transthoracic echocardiography within 24 hours after admission. The primary endpoint was the incidence of systolic dysfunction after Ims-TBI. The secondary endpoint was survival on discharge. Clinical data and outcomes were assessed within 24 hours after admission or during hospitalization. About 23 of 123 patients (18.7%) developed systolic dysfunction after Ims-TBI. Higher admission heart rate (odds ratios [ORs]: 1.05, 95% confidence interval [CI]: 1.02-1.08; P = .002), lower admission GCS score (OR: 0.77, 95% CI: 0.61-0.96; P = .022), and higher admission serum high-sensitivity cardiac troponin T (Hs-cTnT) (OR: 1.14, 95% CI: 1.06-1.22; P < .001) were independently associated with systolic dysfunction among patients with Ims-TBI. A combination of heart rate, GCS score, and serum Hs-cTnT level on admission improved the predictive performance for systolic dysfunction (area under curve = 0.85). Duration of mechanical ventilation, intensive care unit length of stay, and in-hospital mortality of patients with systolic dysfunction was higher than that of patients with normal systolic function (P < .05). Lower GCS (OR: 0.66, 95% CI: 0.45-0.82; P = .001), lower admission oxygen saturation (OR: 0.82, 95% CI: 0.69-0.98; P = .025), and the development of systolic dysfunction (OR: 4.85, 95% CI: 1.36-17.22; P = .015) were independent risk factors for in-hospital mortality in patients with Ims-TBI. Heart rate, GCS, and serum Hs-cTnT level on admission were independent early risk factors for systolic dysfunction in patients with Ims-TBI. The combination of these 3 parameters can better predict the occurrence of systolic dysfunction.

Experimental and numerical characterization of screw elements used in twin-screw extrusion

Hot melt extrusion by a co-rotating twin screw extruder is an important process in the pharmaceutical industry. Especially for quality by design aspects, a comprehensive process understanding is indispensable. The performance of conveying elements was determined as critical process parameter, and therefore an experimental and numerical framework was developed to analyze and compare variations. A test rig capable of measuring volume flow, pressure and torque with high accuracy and precision was designed and built. The 3D simulation was performed using computational fluid dynamics (CFD). A stationary model with impulse transmission and an apparent motion of the screws was applied. The experimental data were fitted to the model of Pawlowski, and parameters for the pressure (A1, A2) and power characteristics (B1, B2) were determined. Good agreement between experimental data and the model was observed. The simulation was significantly faster compared to common methods, and the results were consistent with the literature. Systematic investigations of a native and worn screw were performed with CFD resulting in a transport capacity increase and a pressure build up decrease for all tested screw elements. An experimental and simulation setup was generated to assess the performance of co-rotating twin screw elements. The experiments provided high-quality data, and the simulations exhibited high flexibility with low computational effort.

An apparent motion color illusion.

We introduce a new illusory color phenomenon. The illusion is evoked by two alternating displays comprising various colored disks. Although the colors in the alternating displays are the same, the color appearance of the two displays are quite different. We suggest that apparent motion of the disks modulates the color percepts.

A novel insertional allele of the CG18135 gene is associated with severe mutant phenotypes in Drosophila melanogaster.

Drosophila melanogaster has been at the forefront of genetic studies and biochemical modeling for over a century. Yet, the functions of many genes are still unknown, mainly because no phenotypic data are available. Herein, we present the first evidence data regarding the particular molecular and other quantifiable phenotypes, such as viability and anatomical anomalies, induced by a novel P{lacW} insertional mutant allele of the CG18135 gene. So far, the CG18135 functions have only been theorized based on electronic annotation and presumptive associations inferred upon high-throughput proteomics or RNA sequencing experiments. The descendants of individuals harboring the CG18135 P{lacW}CG18135 allele were scored in order to assess mutant embryonic, larval, and pupal viability versus Canton Special (CantonS). Our results revealed that the homozygous CG18135 P{lacW}CG18135 /CG18135 P{lacW}CG18135 genotype determines significant lethality both at the inception of the larval stage and during pupal development. The very few imago escapers that either breach or fully exit the puparium exhibit specific eye depigmentation, wing abnormal unfolding, strong locomotor impairment with apparent spasmodic leg movements, and their maximum lifespan is shorter than 2days. Using the quantitative real-time PCR (qRT-PCR) method, we found that CG18135 is upregulated in male flies, but an unexpected gene upregulation was also detected in heterozygous mutants compared to wild-type flies, probably because of regulatory perturbations induced by the P{lacW} transposon. Our work provides the first phenotypic evidence for the essential role of CG18135, a scenario in accordance with the putative role of this gene in carbohydrate-binding processes.

Deep learning of Parkinson's movement from video, without human-defined measures

BackgroundThe core clinical sign of Parkinson's disease (PD) is bradykinesia, for which a standard test is finger tapping: the clinician observes a person repetitively tap finger and thumb together. That requires an expert eye, a scarce resource, and even experts show variability and inaccuracy. Existing applications of technology to finger tapping reduce the tapping signal to one-dimensional measures, with researcher-defined features derived from those measures. Objectives(1) To apply a deep learning neural network directly to video of finger tapping, without human-defined measures/features, and determine classification accuracy for idiopathic PD versus controls. (2) To visualise the features learned by the model. Methods152 smartphone videos of 10s finger tapping were collected from 40 people with PD and 37 controls. We down-sampled pixel dimensions and videos were split into 1 s clips. A 3D convolutional neural network was trained on these clips. ResultsFor discriminating PD from controls, our model showed training accuracy 0.91, and test accuracy 0.69, with test precision 0.73, test recall 0.76 and test AUROC 0.76. We also report class activation maps for the five most predictive features. These show the spatial and temporal sections of video upon which the network focuses attention to make a prediction, including an apparent dropping thumb movement distinct for the PD group. ConclusionsA deep learning neural network can be applied directly to standard video of finger tapping, to distinguish PD from controls, without a requirement to extract a one-dimensional signal from the video, or pre-define tapping features.

Top-down biological motion perception does not differ between adults scoring high versus low on autism traits

The perception of biological motion is an important social cognitive ability. Models of biological motion perception recognize two processes that contribute to the perception of biological motion: a bottom-up process that binds optic-flow patterns into a coherent percept of biological motion and a top-down process that binds sequences of body-posture ‘snapshots’ over time into a fluent percept of biological motion. The vast majority of studies on autism and biological motion perception have used point-light figure stimuli, which elicit biological motion perception predominantly via bottom-up processes. Here, we investigated whether autism is associated with deviances in the top-down processing of biological motion. For this, we tested a sample of adults scoring low vs high on autism traits on a recently validated EEG paradigm in which apparent biological motion is combined with frequency tagging (Cracco et al., 2022) to dissociate between two percepts: 1) the representation of individual body postures, and 2) their temporal integration into movements. In contrast to our hypothesis, we found no evidence for a diminished temporal body posture integration in the high-scoring group. We did, however, find a group difference that suggests that adults scoring high on autism traits have a visual processing style that focuses more on a single percept (i.e. either body postures or movements, contingent on saliency) compared to adults scoring low on autism traits who instead seemed to represent the two percepts included in the paradigm in a more balanced manner. Although unexpected, this finding aligns well with the autism literature on perceptual stability.

Berkeley on true motion

Studies of the Early Modern debate concerning absolute and relative space and motion often ignore the significance of the concept of true motion in this debate. Even philosophers who denied the existence of absolute space maintained that true motions could be distinguished from merely apparent ones. In this paper, I examine Berkeley's endorsement of this distinction and the problems it raises. First, Berkeley's endorsement raises a problem of consistency with his other philosophical commitments, namely his idealism. Second, Berkeley's endorsement raises a problem of adequacy, namely whether Berkeley can provide an adequate account of what grounds the distinction between true and merely apparent motion. In this paper, I argue that sensitivity to Berkeley's distinction between what is true in the metaphysical, scientific, and vulgar domains can address both the consistency and the adequacy problems. I argue that Berkeley only accepts true motion in the scientific and vulgar domains, and not the metaphysical. There is thus no inconsistency between his endorsement of true motion in science and ordinary language, and his metaphysical idealism. Further, I suggest that sensitivity to these three domains shows that Berkeley possesses resources to give an adequate account of how true motions are discovered in natural science.